Plasma reaction of group VI metal carbonyls

The hexacarbonyl compounds of Cr, Mo, and W have been used as precursors in plasma-enhanced chemical vapor depositions (PECVD). They form films of good adherence on glass, ceramics, and a variety of polymers. The nature of the deposits depends very much on the composition of the gas, which forms the plasma. When pure argon is used, the resulting films contain considerable amounts of oxygen and carbon. Films deposited in hydrogen/argon mixtures consist of the metal and/or the carbide. With Ar/O₂ mixtures, Mo(CO)₆ and W(CO)₆ are converted into films of MoO₃ and WO₃, respectively. When H₂S/H₂ mixtures are used as plasma gas, Mo(CO)₆ yields films consisting of MoS_x.     

Spin trapping in the interaction between acetylenic hydrocarbons and group VIB metal carbonyls

1-Heptyne and 2-heptyne were reacted with Mo(CO)₆ (M=Cr, Mo, W) under different conditions. All samples exhibit ESR signals only in the presence of spin traps. Both carbon-centered and metal-centered radicals have been observed. The radical intermediates were identified by isotropic g-values and splitting constants for nitrone spin adducts obtained from the reaction systems under various conditions.     

The reaction of neodymium(III) oxide with chromium(III) oxide

The reaction of Nd₂O₃ and Cr₂O₃ in air has been studied in the temperature range 350–950°C. The nature and quantity of products formed was investigated primarily by an analytical scheme developed to permit the determination of the amounts of unreacted Nd₂O₃ and Cr₂O₃ and the amounts of possible products. From 350–600°C the sole product was Nd₂(CrO₄)₃, from 630–840°C the products were Nd₂(CrO₄)₃ and NdCrO₃, and from 880 to 950°C the sole product was NdCrO₃. The variation with temperature of the amounts of products formed at constant reaction time was investigated. The kinetics of the reaction were investigated at the following temperatures, 630, 650, 680, 700, 720 and 760°C. At each temperature, with increasing time the amount of Nd₂(CrO₄)₃ formed increased to a maximum and then decreased whereas the amount of NdCrO₃ formed increased continually. The results together with experiments on the effect of oxygen and argon atmospheres are interpreted as follows. NdCrO₃ is not formed by direct combination of Nd₂O₃ with Cr₂O₃. Instead the reaction of the two oxides produces Nd₂(CrO₄)₃, the thermal decomposition of which then leads to the formation of NdCrO₃. The absence of NdCrO₄ as a reaction product is investigated and discussed as is the absence of NdCrO₃ as a reaction product below 630°C.     

Dinuclear group VIB metal carbonyl complexes bridged by bis(diphenylphosphino)alkanes

Reactions of the intermediate W(CO)₅THF, generated photochemically from W(CO)₆ in THF, with Ph₂P(CH₂) _n PPh₂ [ = PP; n = 2 (dppe), 4 (dppb), 6 (dpph), 10 (dppd)] at room temperature in THF solutions gave exclusively bimetallic complexes of the (CO)₅WPPW(CO)₅ type. In addition, complexes bridged by diphosphine ligands of the (CO)₄(pip)MPPM(pip)(CO)₄ type (pip = piperidine; M = Mo, W) were prepared by stirring the (CO)₄M(pip)₂ complexes with bis(diphenylphosphino)alkanes in CH₂Cl₂ solution at ambient temperatures. These new bis(diphenylphosphino)alkane-bridged complexes were characterized by i.r., ¹H- and ³¹P-n.m.r. spectroscopies, as well as by elemental analysis.     

Photochemical reactions of group VIB metal carbonyls with heterocyclic Schiff bases derived from 4-amino -3-hydrazino-5-mercapto-1,2,4-triazole

The new complexes, M(CO)₅(Schiff base) [M?=?Cr; 1, Mo; 2, W; 3, Schiff base?=?4-salicylidenamino-3-hydrazino-5-mercapto-1,2,4-triazole, SAHMT, a; 4-(2-hydroxynaphthylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole, 2HNAHMT, b; 4-(3-hydroxybenzylidenamino)-3-hydrazino-5-mercapto-1,2,4- triazole, 3HBAHMT, c; 4-(4-hydroxybenzylidenamino)-3-hydrazino-5-mercapto-1,2,4- triazole, 4HBAHMT, d; 4-(5-bromosalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole, 5BrSAHMT, e; were synthesized by photochemical reaction of metal carbonyls M(CO)₆ (M?=?Cr, Mo, W) with new heterocyclic Schiff bases derived from 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, a–e. The ligands and complexes have been characterized by elemental analysis, EI-mass spectrometry, FT-IR, ¹H and ¹³C-{¹H}-NMR spectroscopy. The spectroscopic studies show that Schiff bases, a–e, are monodentate and coordinate via azomethine N donor to the central metal atom in M(CO)₅(Schiff base) (M?=?Cr, Mo, W).     

Tetraazaadamantane derivatives of group VI metal carbonyls

Summary Tetraazaadamantane (taad) reacts with group VI metal hexacarbonyls to give mononuclear (taad)M(CO)₅ (M=Cr, Mo and W) derivatives. Mixed ligand metal tricarbonyls,cis- (L-L)(taad)M(CO)₃ (L-L=o-phenanthroline or 2,2-bipyridine; M=Cr and Mo) have also been synthesised. Bromine or iodine reacts with (taad)M(CO)₅ (M=Cr and Mo) to give [(taad)M(CO)₅X]⁺X^– (X=Br or I). Nitrosyl chloride reacts with (taad)M(CO)₅ at room temperature to yieldmer- (taad)M(CO)₃NOCl while with the mixed (L-L)(taad)-Mo(CO)₃ complex, a mixture of (L-L)Mo(NO)₂Cl₂ and (L-L)Mo(CO)₂NOCl was obtained. An analogous reaction with (L-L)(taad)Cr(CO)₃, gave only (L-L)Cr(NO)₂Cl₂ derivatives. The products have been characterised by elemental analysis, i.r. spectra, conductivity data and magnetic measurements.     

Phase-transfer catalysed substitution of group VI metal carbonyls

The substitution of Group VI metal carbonyls by tertiary phosphines, triphenylarsine or dipyridyl is greatly accelerated by a two-phase system, benzene/ 50% aqueous sodium hydroxide, in the presence of tetra-n-butylammonium iodide as phase-transfer catalyst.     

Reactions of group 6 metal carbonyls with salicylaldehyde isonicotinic acid hydrazone

Sunlight irradiation of the reactions of [M(CO)₆], M?=?Cr, Mo and W with salicylaldehyde isonicotinic acid hydrazone (H₂salnah) in THF were investigated. Interaction of [Cr(CO)₆] with H₂salnah resulted in formation [Cr₂O₂(H₂salnah)₂]. The corresponding reactions of molybdenum and tungsten carbonyls yielded dinuclear oxo complexes [M₂O₆(H₂salnah)]. All complexes were characterized by elemental analysis, IR, mass spectrometry and ¹H NMR spectroscopy. The IR spectra of complexes exhibited bands due to either terminal or bridged metal oxygen bonds. Magnetic measurement of [Cr₂O₂(H₂salnah)₂] showed it has paramagnetic characteristics with high spin d⁴ configuration and μ_eff of 1.27?BM. Electronic spectra of the complexes in DMF displayed visible bands due to ligand-to-metal charge transfer. Thermal properties of the complexes were investigated by thermogravimetry technique.     

Synthesis of (η5-cyclopentadienyl)-η1-(2,4-diphenyl-1-cyclobutenyl-3-thione)dicarbonyliron and its reaction with group VI metal carbonyls

Conclusions A synthesis is reported for the previously unknown thioketone, (⁵-cyclopentadienyl)-¹-(2,4-diphenyl-1-cyclobutenyl-3-thione)dicarbonyliron (II), which was used to prepare new heterometallic binuclear complexes with molybdenum and tungsten carbonyls.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 711–712, March, 1986.     

Reaction of transition metal carbonyls with heterocyclic systems—III: SN2′-type reaction of complexed π-allyl systems

A proposition regarding the capability of a complex π-allyl system to undergo a displacement reaction was advanced (eqn 2) and examined experimentally. A unique structural feature of this system is the four rather than three C atoms which intervene between the displaced and entering groups. The experiment was carried out using lactone 1c which is internally complexed and was properly labelled with deuterium. The product of its reaction with aniline has been found to be rearranged with respect to the D label, thus substantiating an S_N2′-type mechanism in a complexed π-allyl system (eqn 2). From an intramolecular comparison study of the reactivity of an allyl and complexed π-allyl system in S_N2′-type displacement reactions using compound 10, it was concluded that the latter is more reactive than the former. Furthermore, the π-allyl lactone 12, in which the displaced and entering groups are separated by three C atoms, was also found to undergo a displacement reaction.     

Octahedral metal carbonyls-XXIX: Mass spectra of cis-disubstituted derivatives of the group VI-B metal carbonyls

The mass spectra of a number of cis-disubstituted derivatives of the Group VI-B metal carbonyls (M = Cr, Mo, W), in which the substituents are bidentate ligands bonding to the metal through As, S or N donor atoms, have been obtained. The spectra for derivatives of o-phenylenebis-(dimethylarsine) (diars) have been examined in greatest detail. For these latter complexes, competitive loss of carbonyls and diars methyl groups was observed. The proposed use of such competition in the evaluation of metal-carbonyl bond strengths is examined. For complexes containing ethylene-bridged bidentate ligands, ions indicative of the loss of five fragments of 28 mass units from the parent ion, corresponding to loss of four carbonyls and the ethylene bridge, are observed. The question of whether ethylene loss occurs prior to, competitively with or after carbonyl loss is considered.     

The reaction of phenylarsenazo with chromium(III)

The conditions for the reaction between phenylarsenazo (PAA) (2-[(2-arsonophenyl)azoj-7-(phenylazo)-1, 8-dihydroxynaphthalene-3,6-disulphonic acid) and chromium(III) have been studied. A blue 1:1 complex is formed at pH 2.2 on heating the reactants at 100 degrees for 15 min. It has maximum absorption at 635 nm and is stable for at least 24 hr. The molar absorptivity is 3.3 x 10(4) 1.mole(-1).cm(-1). Beer's law is obeyed in the chromium concentration range 0-1.4 mug ml . The reaction has been successfully applied to determination of chromium in alloy steel.